Method and Apparatus for Determination of the Rotor Position of an Electric Motor

A method for determining an angular position of a rotor of an electric motor, said rotor having a defined number of pole pairs, the method comprising the steps of:

• applying to at least one stator winding of the electric motor an electric current having a predetermined pulse pattern and a predetermined pulse duration, said electric current causing the rotor to rotate during the pulse duration by no more than 90° divided by the number of pole pairs,
• measuring an angular acceleration of the rotor, and
• determining the angular position of the rotor from a relationship between the electric current and the angular acceleration.

An apparatus for determining an angular position of a rotor of an electric motor, said rotor having a defined number of pole pairs, the apparatus comprising:

• at least one stator winding receiving an electric current with a pulse pattern having a predetermined pulse duration, said electric current causing the rotor to rotate during the pulse duration by no more than 90° divided by the number of pole pairs,
• an acceleration sensor adapted to record an angular acceleration of the rotor caused by the electric current passing through the stator windings, and
• an evaluation unit cooperating with the at least one stator winding and with the acceleration sensor, said evaluation unit determining the angular position of the rotor from a relationship between the electric current and the angular acceleration.